Read the text carefully paying attention to the words in italics. Answer the following question

Can arch dam be constructed in any site?

Text B Arch Dams

An arch dam is built in a convex arch facing the reservoir, and owes its strength essentially to its shape, which is particularly efficient in transferring hydraulic forces to supports. In the arch dams, stability is obtained by a combination of arch and gravity action. If the upstream face is vertical the entire weight of the dam must be carried to the foundation by gravity while the distribution of the normal hydrostatic pressure between vertical cantilever and arch action will depend upon the stiffness of the dam in a vertical and horizontal directions. When the upstream face is sloped the distribution is more complicated.

An arch dam is curved in plan and carries most of the water load horizontally to the abutments by arch action. The thrust requires that sidewalls of the canyon be capable of resisting the arch forces. So arch dams can be used only in narrow canyons. Practically all arch dams constructed in recent years are of concrete, and only few arch dams have failed, in comparison with the more numerous failures of other types of dams.

The same forces which act on gravity dams also act on arch dams, but their relative importance is different. Because of the narrow base width of arch dams, uplift forces are less important than for gravity dams. However, internal stresses caused by ice pressure and temperature changes may become quite important in arch-dam design.

The simplest approach to arch analysis is to assume that the horizontal water load is carried by arch action alone. Most early arch dams were designed on this basis.

Arch dams must be built on solid rock foundation. Seams and pockets in the foundation and abutments are grouted in the usual manner. Since the cross-section of an arch dam is relatively thin care must be taken in the mixing, pouring and curing of the concrete in order to secure its resistance to seepage and weathering. Concrete is placed by techniques similar to those utilized for gravity dams, usually 5-ft lifts, although I0-ft lifts may be also placed at the upper part of an arch where the section is very thin. A layer of mortar is usually placed between lifts to ensure better bond. Small arch dams are provided with only radial construction joints, while large arch dams have circumferential joints as well. All joints must have keyways and in order to prevent leakage water-stops must also be provided. To minimize temperature stresses, the closing section of the dam is poured only after the heat in the other sections is largely dissipated.